PDA

View Full Version : Total Lunar Eclipse - February 20, 2008



ScienceGiant
2007-Dec-17, 06:29 PM
What? Total Lunar Eclipse

When? Wednesday evening, February 20, 2008

Why? The moon will become engulfed by the Earth’s dark shadow for an hour and 43 minutes during a total lunar eclipse. Weather permitting, the entire eclipse can be seen from eastern and central North America.

So What? “The two-hour phenomenon should be a visual feast. It's also an opportunity for reflection on the wondrous nature of our universe. After all, it's so easy to get swept up in day-to-day worries and it's so hard to acknowledge that we inhabit a speck of a planet in unimaginably vast space. So, take a moment to take it all in this evening if the sky is clear. Then make a pledge to carve more time to peer at the night sky on a more regular basis.” -- South Florida Sun-Sentinel Editorial Board 3/3/2007

Is it safe? Dr. Marc S. Flesher, optometrist at Eye-Site Optical Studio on 2216 N. Congress Ave. in Boynton Beach, advises it is perfectly safe to view an eclipse of the Moon without protection. The brightest object you will see is the full Moon itself, just before or just after the eclipse.

What’s the exact time? The Moon enters Earth's umbra shadow on February 20 at 8:43 PM EST, and the eclipse becomes total at 10:01 PM EST. Totality ends at 10:51 P.M. EST, and the umbral phase ends at 12:09 AM EST on February 21.


Timetable for Wednesday, February 20, 2008 Lunar Eclipse in Boynton Beach, FL
Time Event
7:34 PM Moon begins to enter penumbra, the lightest part of the Earth’s shadow.
8:42 PM First contact. Moon begins to enter the umbra of the Earth’s shadow. The eastern side of the Moon enters the darker part of the Earth’s shadow.
10:00 PM Second contact. Totality begins. The Moon is totally within the umbra of the Earth’s shadow. Note that the Moon does not completely disappear because the Earth’s shadow is not completely devoid of light. This light comes around the edge of the Earth and is bent (refracted) through the Earth’s atmosphere into the umbra of the shadow. It is a dull red or brown color for the same reason that sunsets are red. (Red light can penetrate the atmosphere around the Earth; the blue colors are scattered away).
10: 26 PM Mid-eclipse.
10:51 PM Third contact. Totality ends. The Moon begins to leave the umbra of the Earth’s shadow.
12:09 AM Fourth contact. The Moon completely exits the umbra of the Earth’s shadow. The slight shading of the penumbra should still be visible, however, being darkest on the western side of the Moon.
1:17 AM The Moon completely leaves the penumbra of the Earth’s shadow. The eclipse is over.

What is a lunar eclipse? It’s only at full moon that a lunar eclipse is possible. That’s because it’s only at full moon that the moon can only be directly opposite the sun. Only then can Earth’s shadow fall on the moon. An eclipse of the Moon occurs when the Moon moves into the shadow of the Earth. Because the Moon’s motion in its orbit is from west to east, the eastern side of the Moon enters the shadow first. Because the Moon shines only by reflected sunlight, we see the Moon gradually darken as it enters the shadow.

What’s next? There will be a penumbral lunar eclipse on July 27, 2009, at the time of moonset; it will be difficult to see changes in the Moon's appearance. The next total lunar eclipse visible in Florida will be December 21, 2010.

What causes an eclipse of the Moon? The Sun is a source whose light illuminates the solar system. The Moon normally shines by reflecting the Sun's light. The Earth is an opaque object, so the Earth casts a shadow on the side of the Earth opposite the Sun. As the Moon revolves around the Earth it sometimes moves directly into the Earth's shadow. When this happens, the Sun's light can't hit the Moon and so the Moon appears dark (but not completely dark -- some light is bent by the Earth's atmosphere and this does hit the Moon).

Why does the Moon appear red during an eclipse? The Moon is in the twilight zone. While the Moon remains completely within Earth’s shadow, some indirect sunlight still manages to reach and illuminate it. The small amount of light that does hit the Moon comes around the Earth after bending through the Earth's atmosphere. This light is deep red or orange for the same reason that sunsets are red. Rays of white sunlight passing through the atmosphere are subject to "scattering." Blue light sprays off in all directions (this is why the daytime sky glows blue), but the red light is relatively unaffected, so it continues through.

Why don’t we have an eclipse each month? If the moon’s orbit around the Earth and the Earth’s orbit around the sun were on exactly the same plane, we’d have a total lunar eclipse every month at full moon! But in fact, the moon’s orbital plane is tilted by 5 degrees with respect to Earth’s orbital plane. For this reason, lunar eclipses are far from commonplace. The full moon usually eludes the Earth’s shadow by passing above it or below it. But two to four times each year, the Moon passes through some portion of the Earth’s penumbra or umbra.

Why do science teachers say there are two shadows? Optically speaking, the Sun is an extended source, not a point source. With extended sources the shadow has two regions. The Earth’s shadow is composed of two cone-shaped components, one nested inside the other. The darkest and thus most notable is called the umbra. This is the region in which the Sun’s light is totally blocked by the Earth. Surrounding the umbra is the penumbra. In this region some sunlight is present. The part of the penumbra closest to the umbra is the darkest since from there the solid body of the Earth blocks more of the Sun.

NEOWatcher
2007-Dec-17, 07:29 PM
...Is it safe? Dr. Marc S. Flesher, optometrist at Eye-Site Optical Studio on 2216 N. Congress Ave. in Boynton Beach...
I don't think it takes an optometrist to answer this question... I hope they didn't go out of thier way to get this little ditty. Is his location important to the story? (I sense some palm greasing here):think:

...Why do science teachers say there are two shadows? ...
Why does anyone say that? :lol:

ScienceGiant
2007-Dec-18, 09:01 PM
[QUOTE=NEOWatcher;1134706]I don't think it takes an optometrist to answer this question... I hope they didn't go out of thier way to get this little ditty. Is his location important to the story? (I sense some palm greasing here):think:

:)
Well, yes, Marc is my optometrist. So I didn't go out of my way. But a little more backstory - he is also an incredibly generous individual. When I organized a solar eclipse viewing in Paril 2005, he donated $500 for me to purchase solar eclipse sunglasses for the students of the school district as a give away. As a thank you, I included that question in the press release. So, "palm greasing" = no; publicly recognizing a sponsor = yes.

And since the solar eclipse, I've kept him in the loop for other sky events.

NEOWatcher
2007-Dec-19, 02:11 PM
So, "palm greasing" = no; publicly recognizing a sponsor = yes.
I guess I was a little strong in saying "palm greasing", since it essentially is more of a bribe kind of thinking.
It took some thinking... but maybe "back scratching" would have been more appropriate.

I am happy to hear that it is in recognition though. Too many times, I just see back door advertising to the profit of the media source.

ScienceGiant
2007-Dec-19, 06:32 PM
Hey, if my local Mitsubishi Eclipse dealers wanted to sponsor the eclipse viewing, I would SO give the naming rights to them!!!
People seem surprised that the school district does not underwrite any of the expenses for hosting a star party. HQ just expects us to volunteer...